Alkoxy pyrazolylalkanes

ABSTRACT

DISCLOSED HEREIN ARE COMPOUNDS CONTAINING 1 TO 2 PYRAZOLE RINGS BONDED BY NUCLEAR NITROGEN TO A CARBON ATOM WHICH BEARS ONE SUBSTITUENT SELECTED FROM HYDROGEN, ALKYL OR UP TO 7 CARBONS, PHENYL AND BENZYL, THE REMAINING VALENCE(S) BEING SATISFIED BY 1 TO 2 ALKOXY GROUP8S). ALSO DISCLOSED IS A PROCESS FOR MAKING SUCH COMPOUNDS AND THEIR USE, FOR EXAMPLE, AS UV ABSORBERS, CHELATING AGENTS OR CHLORAL POLYMERIZATION CATALYSTS.

3,808,228 Patented Apr. 30, 1974 3,808,228 ALKOXY PYRAZOLYLALKANES Swiatoslaw Trofimenko, Newark, Del., assignor to E. I. duv Pont de Nemours and Company, Wilmington, Del.

No Drawing. Continuation-impart of abandoned applica- 5 tion Ser. No. 89,134, Nov. 12, 1970. This application June 8, 1972, Ser. No. 260,823

Int. Cl. C07d 49/18 US. Cl. 260-310 R 13 Claims ABSTRACT OF THE DISCLOSURE Disclosed herein are compounds containing 1 or 2 pyrazole rings bonded by nuclear nitrogen to a carbon atom which bears one substituent selected from hydrogen, alkyl of up to 7 carbons, phenyl and benzyl, the remaining valence(s) being satisfied by 1 or 2 alkoxy group(s). Also disclosed is a process for making such compounds and their use, for example, as UV absorbers, chelating agents or chloral polymerization catalysts.

CROSS-REFERENCE TO RELATED APPLICATION This is a continuation-in-part application of application Ser. No. 89,134, filed on Nov. 12, 1970, now abandoned.

BACKGROUND OF THE INVENTION (1) Field of the invention This invention relates to novel compounds containing 1 or 2 alkoxy groups attached through carbon to the nitrogen(s) of 1 or 2 pyrazolyl rings.

(2) Description of the prior art No art is known wherein an alkoxy group is attached to carbon which is directly bonded to a pyrazole nitrogen.

SUMMARY AND DETAILS OF THE INVENTION This invention comprises novel alkoxy pyrazolylalkane R =selected from H, alkyl of up to 7 carbons, phenyl and benzyl,

X and Z=selected from H, alkyl of up to 8 carbons, phenyl, halogen, alkoxy of lower alkyl with the proviso that only one of X or Z can be alkoxy, and 5 5 Y=selected from H, lower alkyl, phenyl, CN, N0 and halogen.

The preferred compounds are dialkoxy monopyrazolylalkanes of the formula:

X/ Z R 5/ \JH (R 0)z(B-I I-N wherein: v

R=lower alkyl, R -=hydrogen or lower alkyl, and X, Y and Z'=hydrogen or lower alkyl.

These compounds are particularly useful as catalysts for the polymerization of chloral homopolymer and copolymers thereof with, say, isocyanates and ketenes. The expression lower alkyl means alkyl of up to 4 carbons.

Process The novel compounds are made by reacting an appropriate pyrazole with an orthoester and the reaction mixture is heated to drive off the alcohol by-product. It is preferred, although not necessary, to conduct the reaction in the presence of a strong protonic acid catalyst which serves to greatly reduce the time for completion of the reaction.

The process comprises reacting the orthoester,

)a, and the pyrazole,

It is preferred to add a catalytic amount of a strong protonic acid. Some of each type of pyrazolylalkane, i.e., dialkoxy monopyrazolylalkane and monoalkoxy dipyrazolylalkane is obtained under all reaction conditions. The relative ratios of the pyrazole and orthoester reactants determine only the amount of and not the nature of the reaction products. It is preferred to employ a molar ratio of pyrazole/orthoester between about 1/2 and 3/ 1. The ratio of l/ 2 especially favors formation of the monopyrazolylalkane. When the monoalkoxy dipyrazolylalkane is the desired major product, it is preferred to have a molar ratio of pyrazole/orthoester between about 1/1 and 3/1, and most preferably about 2/1. Molar ratios outside the range of 1/2 to 3/1 can be employed but no particular advantages result thereby.

By catalytic amount of a strong protonic acid is meant a sufficient quantity to alfect appreciably the rate of reaction between pyrazole and orthoester, and such quantities are generally known to those skilled in the art. It is preferred to use quantities of about 0.05 to 1 g. per mole of limiting reactant. Suitable protonic acids include, inter alia, sulfuric acid; arylsulfonic acids such as p.- toluenesulfonic acid, benzenesulfonic acid, pvisopropylbenzenesulfonic acid and the like; alkylsulfonic acids such as 2-propanesulfonic acid, methanesulfonic acid, ethanesulfonic acid, trifluoromethanesulfonic acid and the like. It is also possible to use a polymeric arylsulfonic acid. Other useful protonic acids and amounts in which they should be employed will be evident to those skilled in the art.

The reaction mixture is heated gently so that the alcohol, ROH, distils off slowly. The progress of the reaction may be followed by measuring the amount of ROH evolved. In some cases a binary azeotrope of ROI-I with the orthoester may form. The temperature of the reaction mixture is governed by' the distillation range of the alcohol, and generally is between about 50 to 200 C. Pressure is generally atmospheric. 7

The pyrazole will generally be an equilibrium'mixture of:

with similar isomers formed in the products.

In the following representation of the reaction mech- P anism, Compound I is the dialkoxy monopyrazolylalkane and Compound H is the monoalkoxy dipyrazolylalkane.

12 (011 N-N 1+ ROH wherein:

R=alky1 of up to 7 carbons,

R =selected from H, alkyl of up to 7 carbons, phenyl and benzyl,

X and Z=selected from H, alkyl of up to 8 carbons, phenyl, halogen, alkoxy of lower alkyl with the proviso that only one of X or Z can be alkoxy, and

Y=selected from H, lower alkyl, phenyl, CN, N0 and halogen.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following examples are illustrative only and are included within the broad scope of the invention.

EXAMPLE 1 1,l-diethoxy-l-pyrazolylmethane (A) and ethoxy bis(1-pyrazolyl)methane (B) A mixture of 34 g. of pyrazole and 74 g. of triethyl orthoformate (both 0.5 mole) was heated at 140-150 and ethanol was distilled out through a Vigreaux column. When 29 ml. had distilled, the pressure was reduced and the product was distilled in vacuo. After a small forerun, the main cut, A, B.P. 60-61/3 mm., n 1.4552 came over in 63 g. yield. A second product, B, came over at 106/2.7 mm., n 1.5100 in 4.5 g. yield.

Product A contained about 20% unreacted pyrazole (by NMR). It was stirred with excess sodium hydride until hydrogen evolution ceased and was then redistilled. Pure A boils at 60/2.5 mm.

Analysis.Calcd. for C H N O (A) (percent): C, 56.5; H, 8.29. Found (percent): C, 56.7; H, 8.52.

Analysis.Calcd. for C H N O (B) (percent): C, 56.2; 'H, 6.29; N, 29.2. Found (percent): C, 56.9; H, 6.36; N, 29.6.

The identity of both compounds was confirmed by HNMR A: doublets at 2.551 (11:25) and 2.811 (I: 1.7), a multiplet at 4.071 plus ethyl multiplets around 6.45 and 8.951 in 1:1:2:4:6 ratio. The -CH quadruplet shows additional splitting 0:18) which disappears when the sample is heated and reappears on cooling. The NMR of B had doublets at 2.101 (1:2.7) and 2.391 (11:13), each split further (J =-0.4), singlet at 2.451, a triplet resolved as two overlapping doublets (1:1.8 and 2.7), a 3.751 quadruplet (1:7) at 6.451 and a triplet (i= at8-961in 2 2;1;Z:2= t 0.

4 EXAMPLE 2 l,l-dimethoxy-l-pyrazol-l-ylethane (A) and l-methoxy- 1, l-bis (pyrazol-l-yl ethane (B) H /C\ CH 50 CH CH;

A mixture of g. (1 mole) of trimethyl orthoacetate and 204 g. (3.0 moles) of pyrazole was stirred and heated along with 0.1 g. of p-toluenesulfonic acid until methanol ceased to distil. After removal of low boilers and pyrazole, two main cuts were taken: (A) B.P. 50-55/3.9 mm., obtained in 84 g. yield and (B) B.P. 98l02/4.5 mm., obtained in 43 g. yield. 1

Fraction (A) was contaminated by about 40% unreacted pyrazole, as shown by NMR. It was stirred with excess sodium hydride and redistilled, to give purified (A), 11 1.4579.

Analysis.-Calcd. for C H N O (percent): C, 53.8; H, 7.74; N, 17.9. Found (percent): C, 53.7; H, 7.77; N, 18.5.

The NMR spectrum of (A), neat, had doublets at 2.401 (J=2.4, further split, 1:0.7), 2.74 (CI =1.7, further split, J=0.7), a triplet-like set of overlapping doublets (J -2.5, J=1.7) centered at 4.071, and singlets at 7.17 and 8.441 in 1:1:1:6:3 ratio.

Fraction (B) solidified on standing and was pure l-methoxy-l,1-bis(pyrazol-l-y1)ethane, M.P. 39-40.

Analysis.Calcd. for C H N O (percent): C, 56.2; H, 6.29; N, 29.1. Found (percent): C, 56.5; H, 6.23; N, 29.0.

The NMR spectrum of (B) had two overlapping doublets at 2.471, a triplet at 3.721 (1:2.0), and singlets at 6.71 and 7.581 in 4:2:3:3 ratio.

EXAMPLE 3 a,o-Dimethoxy-l-benzylpyrazole H CuHt H0 (311 (H3CC)z(5--I I N A mixture of 91 g. of trimethyl orthobenzoate (0.5 mole, 102 g. (1.5 mole) of pyrazole and 0.1 g. of p-toluenesulfonic acid was stirred and heated until the pot temperature reached Distillation of methanol ceased after 20 ml. (0.5 mole) has been collected.

The reaction mixture was distilled in vacuo removing lower-boiling components and excess pyrazole. The residue solidified and was purified by recrystallization from EXAMPLE 4 Dimethoxy-3,5-dimethyl-l-pyrazolylmethane H (HaC O)2C A mixture of 100 g. (1. mole) of 3,5-dimethylpyrazole,

200 g. (1.9 mole) of trimethyl orthoformate, and 1 g. of p-toluenesulfonic acid was stirred and heated until the fraction, B.P. 65-75, ceased to distil. Solid K CO was added and the pot contents were distilled in vacuo. The main cut, B.P. .54-60/1.1 mm, was ob ained in EXAMPLE 5 Methoxybis(3,5-dimethyl-1-pyrazolyl)methane nao-c o-cm H I I H3000 A mixture of 192 g. (2.0 moles) of 3,5-dimethylpyrazole, 135 g. of trimethyl orthoformate (1.25 mole, to 20 make up for the 8:2 MeOH:'HC(OMe) azeotrope, B.P.

65 g. (38%) yield. It was redistilled from NaH to remove traces of 3,5-dimethylpyrazole.

Analysis.Calcd. for C H -N O (percent): C, 56.5;

- 65 C.) and 1 g.of p-toluenesulfonic acid was heated so that the fraction B.P..65 .distilled out vslowly.

When the reaction was over, the pot contents were distilled. After removal of pyrazole a product B.P. 120/ 1.5 mm. came over in 95 g. (50%,) yield. It solidified on standing, M.P. 57-59". It was methoxybis(3,5-dimethyl- 1-pyrazolyl)methane.

Analysis.-Calcd. for C H N O- (percent): C, 61.6; H, 7.70; N, 23.9. Found (percent): C, 62.4; H, 7.67; N, 24.7.

These values indicate contamination by tris(3,5-dimethyl-l-pyrazolyl)methane.

The NMR spectrum had singlets at 3.00, 4.13, 6.50, 7.63, and 7.801 in the correct 1:2:3:6:6 ratio.

The table below shows novel pyrazolyl compounds made using trimethyl orthoformate and various pyrazoles, following the general procedure of Examples 4 and 5. The first column shows the literature pyrazole employed as a starting material with the orthoformate. The second column shows the novel dimethoxy monopyrazolylmethanes and the novel monomethoxy dipyrazolylmethanes.

TABLE Literature pyrazole Novel alkoxy pyrazolylalkanes d-nltropyrazole 1,1-dimethoxy-4-nitr0-1-pyrazolylmethane Meth0XyblS(4-nitr0-1-pyrazolyl)methane.

C-NO: C--N02 r (3H ICIH (3H 3H MeO)zCHN-N M80 CH- NN L J2 4-eyanopyrazole 1,l-dlmethoxy-Hyano-l-pymzolylmethane Methoxybls(4-cyan0-1-pyrazolyl)methane.

r o-0N\ t t f i M 0 HNN M OOH- NN e )zC e k J2 4-ch1oropyrazole 1,1-dimethoxy-4-chloro-1-pyrazolylmethane Methoxybis(4-chloro-1-pyrazoly1)methane.

C Cl f CCl tiJH (EH CH ("DE MeO CHN-N MeOOH- -N--N )2- k J2 4-iodopyrazole 1,1-dlmethoxyi-iodo-l-pyrazolylmethane Methoxybls(4-lodo-1-pyrazoly1)methane.

c-r r o 1 (llfi (JH (3H (IfH M 0 CHNN M00 CH- NN 8 )rk J 4-bromopyrazole 1,1-d1methoxy-4-bromo-1-pyrazolylmethane Methoxybis(4-brom04-pyrazolyl)methane.

C-Br f C-Br ofi ("JH 011 H (M00) z-CHNN M00 0 H- EN-N 3,4,5-trlbromopyrazole-.- 1,l-dim8thoxy-3,4,S-tdbromo-I-pyrazolylmethana.-: Methoxybis(3,4,5-tribromo-1-pyrazolyl)methane.

/Br /Br r BrC fil-Br Br(|3 (J-Br (MeO) zCH--1 l-N MeO-CH- 2 3,5-dlethylpyrazole 1,1-diethoxy-3,5-dietl1yl-l-pyrazolylmethane Methoxybis(3,5-diethyl-1-pyrazolyl)methano.

CH f CH H5020 OCaHa H502? ("J-C2 5 (MeO) 2-0 HN-N MeO-CH- N-N 3,5-diphenylpyrazole..;-..; 1,1-dlmethoxy-3,5-dipheny1-1-pyrazolylmethane..-.;..:... Methoxybis(3,5-dlpheny1-1-pyrazolyl)-methane.

CH f CH HsCu-C (E-CeHu H506? fi IHB (MeH)nCHNN MeO-OH- N-N 2 7 TABLEContinued 8 Literature pyrazole Novel alkoxy pyrazolylalkanes 3,5-di-t-buty1pyrazole 1,l-dimethoxy-3,5-di-t-butyl-l-pyrazolylmethane Methoxybis(8,5-di-t-butyl-1-pyraz0lyl) methane.

a"? f a"? tBu-O C-tBu tBuO C-tBu (MeO)zCH-N-I*l MeO OH NI I 3,5-dlmethyl-4-bromopyrazole-. 1,l-dlmethoxy-kbromo-Bj-dlmethyl-l-pyrazolymethane- Methox ybis (4-bromo-3,5-dimethyl-l-pyrazolyl) methane.

%C Br f %C Br MeC C-Me MeO C-Me (Me):-C H-N--I I MeO CH- Ll l---N 2 3(and/or )-octylpyraz0le 1,1-dimethoxy-S-octyl-l-pyrazolylmethane Methoxybis(3-octy1-1-pyrazolyl)methane.

2 5 r HO C-oetyl H C C-octyl (Me0)z-CB-I I--N MeO CH 2 and/or 1,l-dimeth0xy-5-octyl-1-pyrazolylmethane Methoxybis(5-octyl-1-pyrazolyl)mothane.

CH f OH octyl-0 CH cowl-0 CH (MeO)QCH-I I--I I MeO CHk 2 3,4,5-trlmethylpyrazole 1,1-dimethcry-3,4,5-trlmethyl-1-pyrazolylmethane Methoxybis(3,4,5-trlmethy1-1-pyrazolyl)-1nethane.

%C Me f %C Me MeO C-Me Me-C C-Me (MeOhCH-N-N MeO C H- E-N--I I 2 3,4,5-triphenylpyrazole l,l-dimethoxy-3,4,5-trlphenyl-l-pyrazolylrnethane Methoxybls(3,4,S-triphdnyl-l-pyrazolyl)methane.

C-C @115 f %CCuH5 H5C4-C C-CuHs HxsCsC CCeHs (MeO)nCH-NI I MeO CH- L 2 3(and/or 5)-eth0xypyraz0le 1,L-dlmethoxy-3-ethoxy-l-pyrazolylmethane Methoxybis(3-ethoxy-1-pyrazoly1)methane.

)3 r 2 3 HO C-OC2H5 HO C-0 C2115 (MeOhC H-I I-N MeO CH ---I I 2 and/or 1,l-dlmethoxy-Mthoxy-1-pyrazolylmethane Methoxybls(S-ethoxy-l-pyrazolyl) methane.

)3 r f5 H5C20-C CH H5CzO-C 0-H (Me0)OHNl I MeO CHk--I II I 2 Of course, trimethyl orthoacetate (wherein R =CH according to the process of Examples 4 and 5 yields 1,1- R=CH or trimethyl orthobenzoate (wherein R =C H diheptyloxy-l-pyrazolylmethane and 1-heptyloxybis(1-py- R=CH can be employed in place of the trimethyl razolyDmethane. orthoformate. Other operable orthoesters can also be UTILITY used with pyrazoles as described above to give corre- Both the d al-kox nd the monoalkox ra ol lalspondmg novel compounds. Such orthoesters include, for kanes have balsic z f in la p z dyare instance:

useful as acrd acceptors, e.g., hydrogen halides are aba 2 a -2 2 5)3, when"! 4 m sorbed in reactions where the acids are released. An ex- R=C H ample of such a reaction is one between an acyl chloride C5H5CH3C(OC3H5)3, Wh rem e 5 m 2 5; and an alcohol. The pyrazole ring absorbs strongly in the C H C(0CH wherein R =C H R=CH and ultraviolet region and thus the new compounds are use- C H C(0CH wherein R -=C H,, R=CH fuel as UV absorbers or screening agents.

The dipyrazolyl compounds are useful for chelating transition metal ions such as iron cobalt nickel copper I 5 7 weyl Methoden def orgamschen chemle sauerstofi or zinc and extracting them from solution. The following 'verbindungen Part 3, page 300. In these, the triethyl or l trimethyl g oup can be replaced by other lower alkyl jzzg fif g ggg f chelatmg ablhty of ethoxyblsu Others are readily available by the procedure of Houbengroups by trans-esterification procedures. For example, trimethyl orthoformate gives triheptyl orthoformate EXAMPLE A (wherein R=C7H13, R =H), by reaction with heptyl To a mixture of 19.2 g. (0.1 mole) of eth0xybis(l-pyalcoho Reaction f t i p y orthct r ate with yrazcle 5 razo ybm han 65 ml. of 0.5 M NKOAQ solution and 100 ml. of methylene chloride was added 50 ml. of NH PF solution. The blue nickel complex promptly went into the methylene chloride layer and was isolated by evaporation of the solvent as a blue glass.

The alkoxy pyrazolylalkanes are particularly useful as catalysts in the polymerization of chloral to give homopolymers and copolymers thereof with, for example, isocyanates and ketenes. For instances, chloral containing about 30% by weight of p-chlorophenylisocyanate was warmed to 55 C. and about 0.01-3 rnol percent of the above-described new compounds added. The polymerization was effected by standing at room temperature for 6 hours to several days or by cooling to about C. The polymer obtained is generally soluble in chloroform or toluene and solutions are useful for preparation of fibers, and films. The solid polymers are also useful for pressing films, at about 160 to 250 C., and molded articles. By the use of the product of Example 5, at 0.4 mol percent, the polymer obtained had an inherent viscosity of 1.12 and contained 19% of p-chlorophenyl isocyanate. Polymerization was also effected at 0 to 55 C.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An alkoxy pyrazolylalkane of the formula r -i if- R0 nCN-N k 3 n wherein:

n is 1 or 2,

R is alkyl of up to 7 carbons,

R is H, alkyl of up to 7 carbons, phenyl or benzyl,

X and Z are each H, alkyl of up to 8 carbons, phenyl, phenyl, halogen, or alkoxy of lower alkyl with the proviso that only one of X or Z can be alkoxy, and

Y is H, lower alkyl, phenyl, CN, N0 or halogen.

2. An alkoxy pyrazolylalkane according to claim 1, wherein:

R=lbwer alkyl of 1 to 4 carbons, R =hydrogen or lower alkyl, and

X, Y and Z=hydrogen or lower alkyl.

3. An alkoxy pyrazolylalkane according to claim 1, 1,1- dimethoxy-3,5-dimethyl-pyrazolylmethane.

4. An alkoxy pyrazolylalkane according to claim 1, methoxybis(3,5-dirnethoxy-1-pyrazolyl)methane.

5. An alkoxy pyrazolylalkane according to claim 1, 1,1- dirnethoxy-l-pyrazol-l-ylethane. y

6. An alkoxy pyrazolylalkane according to claim 1, 1,1- diethoxy-l-pyrazolylmethane.

7. An alkoxy pyrazolylalkane according to claim 1, a,a-

dimethoxy-l-benzylpyrazole.

8. A process for making an alkoxy pyrazolylalkane which comprises reacting a pyrazole of the formula Y J; X-G oz m I r r with an orthoester of the formula R C(OR) wherein n is 1 or 2,

R is alkyl of up to 7 carbons,

R is H, alkyl of up to 7 carbons, phenyl or benzyl,

X and Z are each H, alkyl of up to 8 carbons, phenyl, halogen, or alkoxy of lower alkyl with the proviso that only one of X or Z can be alkoxy, and

Y is H, lower alkyl, phenyl, CN, N0 or halogen at a temperature between 50 C. to 200 C.

9. A process according to claim 8, employing a strong protonic acid catalyst selected from the group sulfuric acid, arylsulfonic acid, and alkylsulfonic acid.

10. A process according to claim 9, wherein the protonic acid is p-toluenesulfonic acid.

11. A process according to claim 9, wherein the molar ratio of pyrazole/ester is between about 1/2 to 3/1.

12. A process according to claim 9, wherein the molar ratio of pyrazole/ester is about 1/ 2.

13. A process according to claim 9, wherein the molar ratio of pyrazole/ ester is about 2/ 1.

References Cited UNITED STATES PATENTS 4/1961 Wright 260-309 OTHER REFERENCES NATALIE TROUSOF, Primary Examiner US. Cl. X.R. 

